This invention relates to systems for rapid tooling and production of precision small parts, and more particularly to an improvement in automatic screw machines for manufacturing small parts using a sequence of different machining operations.
The automatic screw machine is one type of automatic machine tool that has been highly developed and is widely used in modern metal and plastic working facilities. The screw machine is usually employed to turn out, at a relatively high production rate, parts smaller than those manufactured using horizontal and vertical turret lathes. Such screw machines are typically horizontal automatics, and may have single-spindle or multiple-spindle configurations. In either machine, the stock to be machined is fed through a hollow machine spindle and collet to extend outwardly toward a 5- or 6-position turret or drum. The turret is indexed to place a desired tool in position and the tool is then fed longitudinally against the end of the rotating workpiece. Drills, reamers, hollow mills and counterboring tools are used for facing, drilling, reaming, forming, knurling and other operations. Usually, two independent cam-actuated cross slides are provided to hold forming, grooving or cutoff tools.
In multiple-spindle automatics, several machine spindles are typically arranged in a circular pattern and indexed in a carrier about a non-rotating turret which carries a variety of cutting tools. Successive machining operations therefore can be performed by the cutting tools as the spindle indexes and progresses around the carrier, and throughput can be increased by concurrent operations at the indexing locations. With such systems the screw machine operator tools the setup for high production by selecting the tools to be used in the machine, precisely adjusting them relative to the stock position at which cutting, forming or another operation is to take place, and making necessary adjustments during operation to compensate for wear during high production runs. The more skilled the operator, the shorter the setup and adjustment time, and the higher the throughput. No matter how skilled the operator, however, tooling operations of this type are not suited for economic manufacture of relatively small quantities. Also the machines are not well adapted for operations on small stock, of the order of 1/4" in diameter.
These factors have imposed restraints on the ability to realize full benefit from state of the art technology in product design. Computer-aided design techniques have now made it feasible to define many products by use of computer hardware and software specially adapted for such objectives. Thus a specific part for an assembly may be designed and checked out thoroughly in relation to other parts in the assembly prior to fabrication of the first prototype using CAD hardware and software. This facilitates the design process, but industry also seeks prototype manufacture within a time frame consistent with the short period in which the design can be generated. Moreover, there is a constant tendency to miniaturize products while improving their performance, further complicating the problem of rapidly making small or preproduction quantities. It is highly desirable, therefore, to have an automatic screw machine for micromachining operations that meets such needs.
A consequence of the fact that a design can be generated and its dimensions and operations can also be specified by using a data processor system is that the mechanical setup procedure for a conventional screw machine introduces a backward step, in that the computer output must be translated to mechanical settings. When part configurations have been digitally specified, a suitable machine tool that can be quickly set up from such data can bypass a substantial part if not all of the mechanical tooling problem. However, the data processing portion of the system should be so arranged that an operator having limited training can develop all needed skills quickly. The operator should be enabled to tool a new machining operation quickly, call forth a wide variety of part fabrication sequences from storage, and readily make adjustments and corrections as needed. These objectives should be accomplished in ways that maintain the needed level of precision in the parts being produced. They cannot readily be met by computerized numerical control systems, because of the complex programming that must be done to set up most such systems in three dimensions for a particular new operation by conventional numerical control techniques.